Explain5 marksStandard
A plant leaf is exposed to light. The guard cells surrounding a stoma actively take up potassium ions. Explain how this uptake of potassium ions leads to the opening of the stoma.
CAIE A Level Biology 9700 · Homeostasis
Homeostasis: explain question
How this question is marked
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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